1. Technical Field
The present invention relates to a lens device and an imaging apparatus including a drive unit detachably fixed to an outer circumference of a lens barrel.
2. Related Art
In a lens device of a shouldered camera, such as an electronic news gathering (ENG) camera, a grip may be detachably fixed to an outer circumference of a lens barrel. In addition, the grip is generally equipped with a drive unit for electrically rotating an operation ring such as a zoom operation ring or an iris operation ring provided on the lens barrel.
The drive unit includes a motor, a reduction mechanism configured to transmit a rotating torque of the motor to the operation ring, and a potentiometer configured to detect a rotation angle of the operation ring. Further, the drive unit is configured to drive the motor until the rotation angle detected by the potentiometer reaches a rotation angle corresponding to a command signal that is input from a controller such as an operation switch provided on the grip.
However, when the drive unit is attached to the lens barrel, the rotation angle of the operation ring should be set to be matched to that of the potentiometer for which a jig or the like is required in order to match the rotation angle of the potentiometer and the rotation angle of the operation ring to each other. For this reason, even though the drive unit is detachable or attachable, the detachment or attachment is not easy.
Therefore, there has been proposed a drive unit configured to match a rotation angle of a potentiometer and a rotation angle of an operating ring by frictionally coupling an output shaft of the motor and an input shaft of the potentiometer, and further driving the motor while idling the potentiometer after the potentiometer reaches one side end of a rotation range thereof so as to rotate the operation ring to one side end of a rotation range thereof (see Patent Literature 1 (JP-A-8-292353) and Patent Literature 2 (JP-A-8-297238)).